The present invention relates to configuration measuring method and apparatus for measuring a configuration of a surface of a sample, specifically, for optically detecting a displacement of a probe due to an atomic force that acts between the end of the probe having a needle fitted to the free end of a cantilever, and the sample surface. More particularly, the invention relates to configuration measuring method and apparatus which are suitable for treating large-size, large-area samples. One example of the configuration measuring apparatus can be constructed by an atomic force microscope.
The atomic force microscope for measuring pits and projections of a sample surface with a precision of nanometers or less has been applied to an increasingly expanding range of fields with the recent years trend toward the higher density and the higher degree of integration in optical disks, magnetic recording, semiconductors, and the like. The atomic force microscope is available in various types such as the optical lever type, the optical interference type, and the critical angle type. Below described with reference to FIG. 5 is an optical lever type atomic force microscope which can be implemented with a very simple construction.
Referring to FIG. 5, a sample 41 is fixedly set on a scanner 44 which is movable in X, Y, and Z directions. A probe 42 supported at one end by a probe holder 43 is positioned on the sample 41.
A light source 45 applies a light beam 46 through a lens 47 to a reflecting surface of the probe 42 on the side opposite to the sample 41. A photodetector 48 is supported in such a position as to capture the light beam 46 reflected by the reflecting surface of the probe 42. The lens 47 is located on the axis that connects the light source 45 and the probe 42 to each other, and condenses the light beam 46, which has been applied by the light source 45, onto the photodetector 48 or to one point in its proximity.
When the probe 42 is put into close proximity to the surface of the sample 41, a deflection is caused on the probe 42 due to an atomic force that acts on the probe 42 and the surface of the sample 41. As a result, the reflection angle of the light beam 46 reflected by the reflecting surface of the probe 42 changes to a slight amount. A displacement .DELTA.Z in the Z direction of the probe 42 is magnified and detected on the photodetector 48 that has captured the light beam reflected by the reflecting surface of the probe 42. While this displacement in the Z direction is being detected, the scanner 44 having the sample 41 set thereon is raster-scanned in the X and Y directions and further vibrated in the Z direction, as shown in FIG. 6, whereby the surface configuration of the sample 41 is measured.
However, in the prior art example as shown in FIG. 5, the scanner 44, on which the sample 41 is fixed, is moved in the X, Y, and Z directions for the raster scanning of the sample 41. Therefore, when the surface of a large-area, large-size sample is observed, there would arise a large inertia force due to the sample's own weight. This makes it difficult to control the scanner 44 on which the sample 41 is fixed.
Further, indeed the atomic force microscope is suited to measure microscopic regions of several tens .mu.m or less square with a precision of nanometers or less, but the atomic force microscope's own magnification is too high to observe larger ranges. For example, in measuring pits such as defects of the sample surface that can be observed by an optical microscope, it would matter to correct the shift between a place that is the actual observation target, and a place that is being actually observed.
Recently, atomic force microscopes are used for evaluation of the configurations of pits of an optical disk with a 30 cm diameter, as well as for evaluation of the gap length of the magnetic head of a cylinder-equipped video head, and for evaluation of electronic components. For these measurements, there is a growing field demand for measuring samples in non-destructive fashion for the purpose of sampling inspections in the production line. However, for the conventional atomic force microscopes, it has been difficult to achieve the measurement without cutting the sample itself into about 1 cm square pieces.